July 14 – The Friendly Red Planet

Today’s factismal: The first close-up images of Mars were sent by Mariner 49 years ago today.

Mars has always fascinated people, from the days when the Bablyonians called it Nergal and blamed it for catastrophes like war, famine, and single-party tickets. Today we don’t blame Mars for our disasters (though we do wonder about the Great Galactic Ghoul) but we are still as fascinated as ever. Is there life on Mars? Can people live on Mars? How many illudium 36 explosive space modulators do they have?

Though the last question is a little silly, the other two are quite serious. In the 1800s, telescopes had finally improved enough for people to see Mars as something more than just a blurry dot; it was now a big, blurry dots. And when people (like Giovanni Schiaparelli and Percival Lowell) see blurry things, they tend to describe things that may or may not actually be there, like the canals of Mars. And those things that get described can lead people to do all sorts of crazy things (like panic over a Halloween joke)

Percival Lowell's drawing of the martian canals (Image courtesy Percival Lowell)

Percival Lowell’s drawing of the martian canals
(Image courtesy Percival Lowell)

The first close-up picture of Mars (Image courtesy NASA)

The first close-up picture of Mars
(Image courtesy NASA)

The only way to stop the panic is to get a good view of what is actually on Mars and the only way to do that is to go there. And, in 1965, that’s exactly what we did. We sent a probe called the Mariner 4 to Mars, where it sent back 22 close-up images; the first images of the red planet. Though none of the images would win an award today, in 1965, they had an Earth shattering effect (but there was no ka-boom). They showed that the Earth wasn’t alone and that there were other planets where people might live.

A close-up of a crater on Mars (Image courtesy NASA's HiRISE)

A close-up of a crater on Mars
(Image courtesy NASA’s HiRISE)

The exploration of Mars continues today. And today they are taking pictures using cameras like the HiRISE (High Resolution Imaging Science Experiment), an orbiting camera that could see a martian newspaper laid out on the ground. If you’d like to take part in the exploration, why not head over to NASA’s HiRISE Public Suggestion Page to tell them where you think the next pictures should be taken, or just to glory in all of the amazing images that have already been captured.

July 13 – Under Stress

Today’s factismal: Eugène Freyssinet, father of the modern highway, was born 135 years ago today.

If you’ve ever looked at a highway overpass being built, then you’ve probably wondered “what are those wires in the concrete and why are they there?” The wires sticking out of the concrete are called tension cables and are there to make the concrete stronger by squeezing it. And the engineer who first figured out why they should be there was named Eugène Freyssinet.

Without prestressed concrete, this is what our highways would look like (Image courtesy Pont du Gard)

Without prestressed concrete, this is what our highways would look like
(Image courtesy Pont du Gard)

Large bridges are nothing new. The Romans had aqueducts (large canals to carry water) that stood 160 ft high and stretched more than 1,000 ft. But their bridges were built from brick and mortar and literally required tons of material in order to keep from breaking apart from the sheer weight of the top sections. If you look at the Brooklyn Bridge, you can see how little had changed in the world of construction between the time of the Romans and the 1800s.

Tension wires sticking out of a prestressed concrete arch; without them, the arch would fall apart. (My camera)

Tension wires sticking out of a prestressed concrete arch; without them, the arch would fall apart.
(My camera)

The reason that large bridges (and buildings and monuments, for that matter) needed so much stone was because most things are very weak when they are being pulled apart (are in tension) but are much stronger when they are being squeezed together (in compression). To understand this, consider the difference between a small pile of sand that you can easily deform with a finger and the same pile of sand stuffed into a rubber balloon where it takes a lot more strength to change its shape.

Though a lot of people knew about this effect, it took Eugène Freyssinet to develop a way of applying it to the real world. He discovered that by stretching wires out and casting the concrete around them, he could prestress the concrete and make it much stronger. As a result, he was able to build bridges that were longer and stronger than anything that was ever done before.

The TWA Flight Center at JFK (Image courtesy Ton Stam)

The TWA Flight Center at JFK
(Image courtesy Ton Stam)

And his discovery wasn’t limited to bridges. If you’ve ever seen the TWA Flight Center at JFK airport, or the LAX airport, or the Sydney Opera House, then you have seen prestressed concrete at work.

If you’d like to explore more, or search through thousands of other science topics, then why not look over the National Science Data Library? It is a free website with education plans for teachers and fun facts for everyone else!

July 12 – What A Croc!

Today’s factismal: A female Nile crocodile determines the sex of her children by changing the temperature of the nest; too hot or too cold means more girls!

When Alice went to Wonderland, she recited a poem about Nile crocodiles; the poem praised their “shining scales” and “gently smiling jaws”. But what she should have praised was their ability to determine the gender of their children. As is the case with many other reptiles, the Nile crocodile can change the sex of its children simply by changing the temperature at which the eggs are incubated. If the eggs are kept between 89.1°F and 94.1°F, then the babies that hatch are male. But if the eggs stay too cold or too warm, then the babies that hatch are female.

A baby Nile crocodile hatching (Image courtesy Africa Wild Trails)

A baby Nile crocodile hatching
(Image courtesy Africa Wild Trails)

This would normally just be an interesting and somewhat puzzling phenomenon; biologists could (and have) argue for years over why such a mechanism for determining the sex of the offspring is necessary. But the world is currently undergoing something of a heat wave. The past fifteen years have been stuck on “hot” and the next few decades don’t look much better. And what that means is that the Nile crocodiles will have a harder time keeping their eggs in the temperature range needed for male hatchlings. In effect, the number of male Nile crocodiles will serve as a proxy for the temperature.

And Nile crocodiles are far from being the only critters that will change as the climate does. Trees will sprout further up on mountains, and butterflies will migrate earlier in the year. Flowers will bloom earlier or later. And even fish may change their spawning in response to changes in the climate.

Naturally, phenologists (scientists who study the timing of natural events) would love to record all of these changes. But Nature has the phenologists out-numbered eleventy billion to some. And that’s where you come in. If you would like to spend a little time each week observing the flowers in your backyard or the birds in your neighborhood or any other regular natural event, then the folks at the National Phenology Network would like you to become a Nature Observer! Just mark down your observations and add them to the easy-peasy web form and watch as the phenologists use your data!

July 10 – Go Climb A Tree!

Today’s factismal: There are 411 different types of cell in a healthy adult human.

In science, the interesting questions are always the weirdest ones. They are interesting because (1) most people understand that importance of the question once they hear it and (2) few people would have any idea of how to answer the question. “How many different types of cell does a healthy adult human have?” is one of those questions. It is important because the different types of cells do different things in the body and knowing the relative number of different types of cell with similar characteristics can tell us much about that characteristic’s importance. For example, 145 of those 411 different types of cell are types of neuron; obviously, thought is an important part of the human biological makeup!

So the question is clearly important, but how do we answer it? How can we know how many different types of cell a healthy adult human has? Did they go out and pick apart a politician, putting each cell type into a different pile? Sadly, no (the politicians objected). Instead, the researchers used a technique known as cladistic analysis. They looked over different tissue samples from dozens of different donors and were able to identify features that each cell type had in common. For example, mitochondria were present in most cells so the list was divided into those cells with mitochondria and those without; it “branched” at that point. The cells without mitochondria can further be broken down into those without nuclei and those with.

A tree of life cladogram (Image courtesy American Museum of Natural History)

A tree of life cladogram
(Image courtesy American Museum of Natural History)

Because a written list of all of these differences would be very hard to read (and even harder to keep track of), most scientists instead draw it as a tree-like structure known to geeks as a cladogram (“branch drawing”). You are probably familiar with the “tree of life” which was made in the same way as the tree of human cells. Once the scientists run out of meaningful differences between the different branches, the cladogram in complete and you can find out how many different types of thing there are by simply counting the branches.

Even better, the relationships between the branches often tell us a lot about how things are related. On the tree of life, we know that mammal (like us) are more closely related to lizards (like politicians) than they are to green plants (like broccoli). Those relationships can then help us understand things like “will this heart medicine be dangerous for my kidneys?”

Of course, making these cladograms takes time and effort, but it can be fun. If you’d like to get in on the fun, the folks at Citizen Sort have developed a series of sorting games that you can do to actually sort out data that they will use to understand more about biology. To get in on the fun and games, head over to:

July 7 – What A Stench!

Today’s factismal: In 1855, Michael Faraday wrote a letter to the editor about pollution in the Thames River.

We often think of pollution as being a modern problem, but the truth is that the world is a lot cleaner now than it used to be. Though the Cuyahoga River did famously catch fire in 1969 (and at least a dozen times before that), it and other rivers in the USA have since been cleaned up and now support vibrant ecologies. Air pollution has decreased over the past three decades (with the notable exception of CO2), and ground water contamination is less common than ever.

But in the 1800s, things seemed to be headed the other way as the Thames River demonstrated. Thanks to a rapid increase in industrialization coupled with a laissez-faire approach to waste treatment (which at the time mostly meant “dump it in the river and hope it doesn’t float”), the amount of sewage in the Thames River had jumped sharply. In addition to the offal, blood, and manure being put into the river by meat packers, there was runoff of dyes containing lead and other heavy metals from the fabric makers, and (worst of all) the combined effluent from more than a million people who had toilets but no plumbing in their homes.

A political cartoon showing Faraday giving his card to the river Thames (Image courtesy Punch)

A political cartoon showing Faraday giving his card to the river Thames
(Image courtesy Punch)

In 1855, the well-respected researcher Michael Faraday wrote a letter to the Times about the state of the Thames. (It is almost a shame that he wrote only once; if he had written nine times more, then we could say that “Faraday wrote ten times to the Times about the Thames”.) And just three years later, a combination of a heat wave and drought would create what the British called with characteristic understatement “The Great Stink”. These events led to the development of a modern sewer system in London which then created a decrease in both the odor and (more importantly) the number of cholera deaths.

Of course, getting rid of pollution isn’t something that just happens. It takes a dedicated group willing to report on the water quality of their local stream, river, or wetland. If that sounds like something that you’d like to do, then why not join one of these programs?
Georgia Adopt-A-Stream
Klamath Riverkeeper
Loudoun Stream Monitoring
Missouri Stream Team Program
OPAL Water Survey (England)

July 6 – Oh Baby, Baby!

Today’s factismal: In 1847, a woman was ten times more likely to die of puperal fever if she gave birth in a hospital.

One of the great paradoxes of the 1800s was the deadliness of doctors. Though they were dedicated to healing the sick and helping the ill, there were some circumstances where they seemed to do more harm than good. One of the most notorious of these was childbirth. If a woman gave birth at a hospital, then there was as much as a 30% chance that she’d die of puperal fever; also known as “childbed fever”, it was an infection that typically led to a deadly buildup of toxins in the blood. But if a woman gave birth at home, then there was only about a 3% chance of puperal fever.

When ten times more patients die in the hospital than at home, you’d think that the doctors would sit up and take notice. And they did. Doctors dismissed the idea that they could be the cause (in the words of one expert, “Doctors are gentlemen, and gentlemen’s hands are clean”) and instead suggested that the problem was the proximity to other patients or the lack of fresh air or poor nutrition on the part of the women. It wasn’t until Ignaz Semmelweis compared the mortality rate for hospital wards with midwives to that for wards where doctors delivered babies that the doctors were pinpointed as the cause. Because germs hadn’t been discovered yet, all Semmelweis could do is suggest that “cadaverous particles” were being carried by doctors as they went from autopsies to birthing rooms (yes, things were a lot looser back then).

To prove his hypothesis, Semmelweis started requiring that doctors wash their hands in a chlorinated lime solution (roughly equivalent to a weak bleach) before attending a pregnant woman. Overnight, the incident rates for puperal fever dropped to the same levels seen when women gave birth at home. And for ten years, Semmelweis tried to convince other doctors to follow his lead.

Needless to say, the medical establishment didn’t appreciate the news that they were the cause. The local doctors arranged to have Semmelweis fired and convinced his wife to have him committed to an insane asylum. In an ironic twist of fate, he died of sepsis just two weeks after being admitted, probably due to a beating that the guards had given him. But within two decades Semmelweis would be vindicated. Pasteur would conclusively demonstrate that most diseases are caused by germs; much of his early work focused on puperal fever and relied on Semmelweis’ insights.

Of course, doctors are still trying to learn more about diseases today. And they have learned from past experience and have somewhat more open minds than they did in the 1850s. What that means is that they are now asking for insights from people like you. At the Health Tracking Network, they’d like you to tell them about any symptoms you have (or don’t) relating to colds, the flu, or the stomach flu. Even better, you’ll earn money for charity by participating, which makes this a win-win-win. To participate, head over to


July 5 – Mountains Out Of Molehills

Ever wonder what makes the Ring of Fire, the Ring of Fire? Mary, Peter, and Daniel did. Join them as they discover the answer in today’s Secret Science Society adventure!



Peter and Mary were not jealous of much, but they looked at the pictures from Daniel’s vacation to Colorado with envy. While they had stayed at home over spring break, Daniel’s family had gone to the mountains to ski. And the first day back at school, he showed pictures from the trip to Mary and Peter over lunch.

“I can’t believe that it is so snowy there!” Mary said.

“Yeah,” Peter added. “And the mountains are so tall! Is it really a mile high there?”

“Yes, it is,” Daniel replied. “There’s even a step on the capitol building that tells you when you are a mile above sea level.”

“Cool! I wonder what made the mountains?” Mary asked.

“I don’t know, but I know who will,” Peter said.

“Mr. Medes!” all three chorused.

“Let’s go ask him!” Mary said.

The three friends cleared their lunch trays and then went down the hall to Mr. Medes’ classroom.

“Ah! A salubrious spring to you!” Mr. Medes greeted them. “What brings three such avid explorers to my room on a bright, sunny day?”

“We were looking at pictures of the mountains in Colorado,” Daniel said. “And we wondered what makes mountains.”

“That happens to be an excellent question!” Mr. Medes replied. “Would you believe me if I told you that grandparent’s didn’t know the answer but we do?”

As the three friends shook their heads, he went to the supplies cabinet and brought out two sheets of paper and a shaker of salt. He put the paper on the table, forming an “X”, and then spread a layer of salt about an inch thick over one side of the X.

“It is true,” Mr. Medes continued. “Until very recently, we thought that the surface of the Earth was just one big piece and stuck in one place. But then we discovered that it is broken into more than a dozen smaller pieces that move around very slowly. Those pieces are called”

“Plates!” Peter interrupted. “And they float on magma!”

“Well, you are right about them being called plates,” Mr. Medes replied. “But they don’t float on magma. Magma is molten rock and the outer part of the Earth is solid. But it oozes under pressure, sort of like bubble gum or fudge, which is why those plates can move around5r.”

“Oh. I guess the movies got that bit wrong,” Peter said, abashed.

“Movies usually do,” Mr. Medes smiled. “But as those plates glide along on the outer part of the Earth, which we call the mantle, they either move apart from each other, move beside each other, or run into each other. Now what I’ve done here is create a model that we can use to simulate how those plates move. Here’s how we’ll do the experiment. Daniel, you’ll hold the piece of paper that is on the top so that it cannot move. Mary, you’ll pull on the far side of the piece of paper that is underneath, so that it moves toward the other piece of paper. So those two pieces of paper are two plates moving on the outside of the Earth and that salt on top is like the crust of the Earth and will move with the plates. Got it?”

Seeing everyone nod, he continued. “Now what we have to do is to predict what will happen when the bottom plate runs into the top plate. Peter, what do you think will happen?”

“The sediment will stay in one place and slide off of the plate,” Peter replied.

“No,” Mary said. “You are wrong. The sediment will go under the top plate.”

“I don’t think that will happen,” Daniel said. “I think that the sediment will get scrunched up.”

Well, there’s only one way to find out,” Mr. Medes said. “Let’s move the plates!”

What do you think will happen? Do the experiment!


As Daniel held the paper on top still, Mary slowly pulled the bottom paper. As the far side of the “X” got longer, the other side got shorter, and the salt began to move together. At first, it didn’t look as if anything was happening. And then, as the three experimenters watched, the salt began to pile up and make hills and mountains.

“Wow!” Peter exclaimed. “The salt did pile up!”

“That’s right,” Mr. Medes said. “And that is the secret to orogeny, or mountain building. As the plates move together, the sediment gets squished up to form a great big mountain. Almost every large mountain chain was formed this way; the Himalayas, the Rockies, the Andes, the Alps all were made when one plate crashed into another.”

“And Hawai’i, too?” Mary asked.

“Actually, Hawai’i is a special case, just like Iceland and Yellowstone” Mr. Medes replied. “It was formed a different way, when a big blob of magma hit the bottom of the plate and melted its way through. And then there is the longest mountain chain in the world, the Mid-Atlantic ridge. It was formed when plates moved apart. But those are exceptions. The rule is that mountains are made when two plates crash together, just as most dents are made when two cars crash.”

“Gosh,” Daniel said. “So I was standing an old accident site!”

“Actually, the crash that made the Rocky mountains is still going on,” Mr. Medes replied. “The plates are still moving around. The Rockies were formed when the North American plate hit the Farallon plate. Normally, you’d get the mountains made very close to the coast, like the Cascades, the Aleutians and the Andes. But, because the Farallon plate went under the North American plate at such a shallow angle, it made the mountains very far inland.”

“Don’t the Cascade mountains and the Aleutians have lots of volcanoes?” Mary asked.

“Yes, they do!” Mr. Medes said. “And that is because of those plates. You remember how you predicted that the sediment would go down with the plate?”

“Yes,” Mary said. “I guess I was wrong.”

“Not entirely,” Mr. Medes replied. “Though most of the sediment stays up on the surface, some gets stuck on the plate and moves down into the mantle. And that sediment is chock full of water and limestone. When the sediment gets into the mantle, it releases that water and the carbon dioxide from the limestone. That gets into the surrounding mantle rocks and makes them melt, just a little. That new, hot magma goes up and erupts on the surface as a volcano. That’s why there are so many volcanoes around the Pacific rim and why we sometimes call it the ‘ring of fire’.”

At that moment the bell rang, signaling that it was time for class.

“Speaking of ringing,” Daniel said. “It is time for class. See you guys later!”